A subdomain is a web address, that is under a main, or a root domain name. An illustration is something.domain.com, where domain.com is the main domain address, while "something" is the subdomain below it. Every subdomain can have its own website and records i.e. apart from employing the domain name as a part of the whole web address, a subdomain can be totally independent and also hosted by a separate service provider. Using a subdomain can be quite handy if you'd like to have different sites which are associated in some way. For example, you could have an on-line store under the main domain plus a forum under a subdomain in order to supply means for your clients to ask questions and / or share opinions concerning your products. The benefit of using a subdomain as opposed to a subfolder is that the web sites will be separated, so you're able to update one of them or perform maintenance without affecting the other.